Substituted benzo-naphthyridines which are distinguished by a pronounced inhibition of blood platelet aggregation are described in DE-OS 21 23 328 and in U.S. Pat. No. 3,899,494. The use of the compound with the proposed INN benafentrin, which falls under these protective rights, as a bronchodilator and for the treatment of inflammatory diseases of the respiratory tract is disclosed in European Patent Application 247 971.